It's titanium nitride (not nitrate) and it's applied by PVD...basically it's evaporated onto the surface of the part. The traditional reason it wasn't applied to Al parts is that the process temperature would ruin the aluminum heat treatment...not sure how they got around that. Maybe there's a special (lower temp) process. The other issue is that it's only ~3 microns thick and usually needs a hard substrate (e.g. tool steel) to support it. Maybe they're putting it on top of hard coat anodize...